In a conventional inkjet printer, a printhead has a series of actuators out of which the printing fluid or ink ejects to an image receiving substrate. The ink drop mass, or size, and drop speed, or velocity, can influence the quality of the printing. Further, a variation in drop speed across the series of actuators can affect the quality of the printing, as drop speed variation can lead to poor image quality. The drop speed variation of an actuator due to actuation of neighboring actuators is known as crosstalk.
Conventional membrane-based inkjet printers rely on a two-part process for jetting: first, ink is drawn into the actuator when a membrane is electrostatically pulled down; and second, the ink is ejected from the actuator nozzle when the membrane is released. The pulldown and release is achieved by applying an amplified square waveform to the actuator. In particular, the square waveform comprises a high voltage that acts to pull down the membrane and fill the actuator with ink, followed by an application of 0 V to release the membrane and eject the ink. During the application of the square waveform, a pressure transient is transmitted to the ink feed behind the actuators, which affects the amount of pulldown of neighboring membranes, which in turn causes the ink drop speed to vary across the actuators.
Furthermore, the membranes in actuators conventionally include a dimple of uniform height that runs along the entire length of the membrane. The dimple can come to rest on a landing pad when the membrane is pulled down to prevent the membrane from contacting electrodes that transmit the voltages to the actuators. When the dimple comes to rest on the landing pad, a high electrical field can develop and damage to the actuator can occur.
Thus, there is a need for a voltage wave form that reduces pressure transients across the series of actuators and prevents the membrane from excessively pulling down. Further, there is a need for a dimple implementation to reduce conditions that lead to damage to the actuators.